FAQ — 30 Common Questions

Compost is the stable, humus-rich product of controlled aerobic decomposition of organic matter. It is not manure, not a fertilizer, and not just "rot" — it is a managed microbial product with defined properties (maturity, stability, C:N, nutrients). See The Science.

For most field situations compost wins on handling, odor, weed seeds, pathogens, and slow-release nitrogen; raw manure wins on nutrient load per tonne moved and lower process cost. Manure's nitrogen is immediately plant-available but easily lost; compost's isn't available until mineralized (see here and the comparison table). Many operations use both deliberately.

Aerobic decomposition (with oxygen) is fast, hot, and produces CO₂ and water; anaerobic decomposition (without oxygen) is slow, cold, odorous, and produces methane, volatile fatty acids, and amines. Composting is explicitly aerobic — the whole process chapter is about keeping it that way.

Managed windrows: 8–16 weeks active + 4–8 weeks curing. Aerated static piles: 3–6 weeks active. In-vessel: 1–4 weeks plus curing. Vermicomposting: 2–6 months after pre-composting. Passive piles can take 6–18 months. "Finished" means stable and mature — see stability vs maturity.

25:1 to 40:1 (with ~30:1 a common sweet spot). Below ~20:1 you lose nitrogen as ammonia; above ~40:1 decomposition crawls. Use the interactive calculator to plan blends.

For up to a few hundred tonnes a year, a turned windrow or loader-built pile with good surface management is cheapest and most forgiving. Wet or odorous feedstocks push you toward an aerated static pile. The comparison matrix walks through the trade-offs.

In a well-run hot system, yes, in small amounts — but meat and dairy are vectors for flies and odors if not buried deep in an active pile. Most on-farm systems either exclude them or route them through bokashi fermentation first. Large-scale food-scrap operations use covered aerated systems for a reason.

Yes, if the pile is big enough (typically ≥2 m high, large footprint) and made with fresh, moist, N-rich material. Small piles freeze solid; large ones generate heat through the coldest weeks. Details in why piles fail to heat.

Bokashi is fermentation, not decomposition: lactic-acid bacteria pickle food waste in a sealed bucket at ambient temperature, producing an acidic pre-compost that must be buried or finished in a hot pile. It handles meat/dairy with no odor and no infrastructure — see the bokashi section.

Turn when the core temperature peaks and starts to fall — roughly every 7–10 days in the first month, every 2–3 weeks after, then stop for curing. Turning schedules are triggers, not calendars: see turning strategy.

Five usual suspects: too dry (<40%), too wet (>65%), C:N too high, pile too small (<1 m³), or the material was already decomposed. Work through the diagnostic.

That's anaerobic decomposition: the pile is oxygen-starved, almost always because it's too wet or too compacted. Turn immediately with dry, coarse carbon (straw, chips), rebuild no taller than 2 m, and cover against rain. See odor troubleshooting.

The squeeze test: a handful should feel like a wrung-out sponge — damp, holding shape, no dripping water (50–60%). Too little crumbles, too much drips. See moisture management.

Rarely, but yes — huge, dry, compacted piles above ~70 °C can self-ignite. Prevent with turning, pile sizing, and probe monitoring; if you see internal smoke, pull the pile apart and wet it thoroughly. See fire risk.

They're breeding in exposed fresh food scraps or manure on the pile surface. Cap every fresh addition with 10–15 cm of hot material or browns, keep receiving areas small, and maintain active hot cores — see vector management.

Field-crop maintenance rates: 2–6 t/ha/yr dry matter (≈10–30 t/ha as-applied), capped by soil-test phosphorus. One-time soil-building rates up to 50–100 t/ha are used in reconstruction projects. Calculate precisely with the rate calculator.

Just before planting or at main tillage, or in fall for spring crops on well-drained soils. Incorporate within 24–48 hours where possible; never spread on frozen, saturated, or snow-covered ground (setbacks and timing in Field Application).

No. Compost supplies some N (10–40% available year 1), a lot of slowly released P and K, and broad micronutrients — but for high-demand crops you still budget mineral N. Its real job is soil function: structure, water, and biology (the benefits chapter).

Aerated compost tea is mature compost extracted in aerated water — a microbial + humic inoculant, not a fertilizer or pesticide. Evidence shows modest, inconsistent disease and growth effects. Brew aerobically from tested compost and use promptly. Full primer: Compost Tea.

Yes — screened, mature, low-EC compost at 10–30% by volume in a peat/bark blend makes an excellent media component. Test each batch for salt (EC) and germination; compost alone is too dense and too salty for containers. More on screen sizes, blends, and stockpile care in Screening, Finishing & Storage.

Fresh, immature compost can — ammonia, organic acids, and salts injure seedlings (that's why maturity testing exists). Cured, mature compost is safe at normal rates. High-salt composts and heavy fresh rates on dry soils are the usual culprits when crops "burn."

Four checks: (1) temperature has returned to ambient and stays there; (2) it no longer smells and is dark and crumbly; (3) a stability test (e.g., Solvita ≥6) says low respiration; (4) a germination test says it's non-phytotoxic. Details in Quality & Standards.

Properly managed thermophilic composting (55 °C+ sustained, whole pile) kills most human pathogens and weed seeds — this is what the time–temperature standards are for. A minority of hard-coated seeds and some plant pathogens survive, so hygiene and rotation still matter. See pathogen reduction.

Yes, and they're one of the most common serious compost problems: aminopyralid-family pasture herbicides survive the animal, the manure, and the compost pile, then damage tomatoes, beans, and other sensitive crops. Bioassay unknown feedstocks — see the horse-manure and bioassay sections.

Both concentrate as carbon is consumed. Heavy metals are a feedstock problem (biosolids, industrial byproducts); PFAS enters mainly via biosolids and some food-contact materials. Clean feedstocks are the only real control; test if you're selling into sensitive markets. See contaminants.

Yes, if made to NOP requirements — for raw-manure compost: initial C:N 25:1–40:1 and 55–77 °C for 15 days with ≥5 turnings (or equivalent static process), with compliant feedstocks (no biosolids). Keep the temperature logs. See standards.

Well-run aerobic composting emits mostly biogenic CO₂ plus small methane and nitrous oxide; badly-run piles emit much more of both. The climate win comes from diverting organics from landfills (large methane avoided) and from soil carbon gains on application. See GHG management.

Site on an all-weather pad with 2–4% slope, keep clean water off the working area, contain and reuse or treat pad runoff, and respect setbacks. The full watery checklist is in Environmental Impact.

Usually yes when it replaces an existing cost (hauling water-heavy manure, bedding purchases, disposal fees) or creates a sellable product near markets; marginal on fertile high-OM soil when done just "for fertility." Cost it against your real alternatives — see Economics & Logistics.

In the US, USDA-NRCS EQIP funds Composting Facility (CPS 317) practices — pads, turners, covers — and many states and provinces have manure/compost incentive programs. Local conservation districts are the fastest route to current funding. More in regulatory & policy costs.